Footprints

I was about to head out the front door today and brave the newly fallen snow when my eye caught these footprints. "The postman's been" I thought, but there was nothing in the porch.

Then I noticed that the footprints approached the door but then stopped.

"What the hell" I thought. "I wonder was that alien paying me a visit but his spaceship came back just before he could reach my door? Had he changed his mind about going home and decided to seek asylum with me, as the only person who was aware of his existence? And got caught short, so to speak?"

Or was it a different story entirely. "Surely" I thought "my new vaporiser burglar alarm could not be so efficient as to vanish a burglar without trace on my doorstep?"

Then I noticed the curve. Whoever it was had come close to the door and suddenly turned on their heel. "What" I wondered "had frightened them away"

Then the penny dropped. Thank God for some literate and conscientious junk-mailers.